ABSTRACT Infrared thermography is an excellent

investigative tool used for a multitude of building-specific applications including roof investigations Since its introduction in the 1970s lower prices and technology advances have allowed thermography to expand becoming an indispensable tool for roof investigators For roofing applications thermography is typically used for condishytion assessment and forensic studies of the low-sloped roof Since many papers have been written on this subject this article will summarize the discussions on how infrared thermography works as a tool for roof invesshytigations1-6

INTRODuCTION Infrared has been around long enough

that many professionshyals use infrared analshyysis for building applishycations including low-slope roof inspections Before the use of infrashyred roofing professionshyals had to go to great lengths to detect leaks caused by moisture intrusion though elecshytrical methods were available for determinshying roof leaks The use of infrared imagers in detecting roof leaks has provided the roofshying industry with a tool

that has become essential to low-slope roof leak inspections

In the past time and resources were used to carefully inspect all areas of the roof below and above to determine if it was leaking or to locate an intrusion site For the trained roof thermographer now a roof overview can be as simple as a quick flyover though onsite inspections are important to confirm any flyover findings7-9 For building owners advances in technology have made infrared imagers one of the most cost-effective ways to detect and locate damshyaging roof leaks and to provide corrective measures

In 1990 ASTM C1153 Standard Practice for Locating Wet Insulation Using Infrared Imaging was published and is still in use with very few changes today10

Unfortunately while imagers have improved dramatically the approaches to roof inspecshytions have not as demonstrated by the minor changes of the current version (ie 2010) of ASTM C1153 One neglected aspect of this standard is that it only describes night investigations It is clear from many years of experience that the laws of physics apply to day surveys as well4

Understanding and using thermography to detect a roof leak or wet insulation is much more difficult than just pointing and shooting a thermal imager Experts need to spend many months as active thermograshyphers and go through many hours of trainshying to achieve competency In the hands of a trained professional though roof leaks can be detected in a variety of ways using infrared thermography

Figure 1 ndash Infrared radiation is emitted from the roof surface and detected by the infrared imager that converts the invisible infrared to a visible image

a u g u s t 2013 I n t e r f a c e bull 11

Figure 2 ndash Wider-angle multiple-image view

pled with the imagerrsquos elecshytronics can yield thermal patterns on the surface of the roof being inspected

IMPORTANT IMAgER SPECIFICATIONS11

In order to capture and interpret the thermal image it may not be necessary to fully understand how the imagerrsquos internal components work or the need to adjust the parameters for correct temperatures However when purchasing it is important to understand some of the basic specificashytions of the infrared imager The two most important specifications are image resolushytion and thermal sensitivity Image resolushytion is very important when observing the roof from a distance as when performing a flyover or from an adjacent building to provide clear images to the client Thermal sensitivity is important when little temshyperature variation is present and a higher contrast is needed

Most infrared imagers applicable for roof inspections have an image resolution of at least 320x240 (76800 pixels or 007 megapixels) though lower resolution can still provide the majority of details to resolve moisture locations provided one is close enough Unfortunately 007 megapixels is much less than the digital cameras we use to visually document the inspection

Figure 3 ndash Narrower single-image view

hOW DOES IT ldquoSEErdquo ThE lEAk The roof emits infrared radiation

according to the laws described by Planck Stefan-Boltzman and Kirchhoff An infrared imager converts invisible infrared radiation into a visible image by detecting the incomshying infrared electromagnetic energy and intensities from the roof with its detector

Just as in visual photography the infrashyred electromagnetic energy is focused with a lens onto a detector which then proshycesses the information into a visual image displayed onto the viewfinder as shown in Figure 1 The intensity of the radiation cou-

Higher resolutions are needed when greater distances are are involved in observing the roof such as in a flyover For this applicashytion to compensate for a lower-resolution imager a telephoto lens is sometimes used and images are stitched or merged together One way to increase resolution as well as wider viewpoint is to stitch multiple images together In Figure 2 three images were stitched together to show a wider viewpoint and higher resolution as compared to the single image shown in Figure 3

For on-roof thermography where close distance observation is performed some thermographers use a wide-angle lens This like stitching increases viewing angle facilshyitating a larger instantaneous viewing area of the roof surface The wide-angle lens can minimize the scan area and the need for multiple images

The thermal sensitivity or noise-equivalent temperature difference (NETD) for an infrared imager is measured in degrees Celsius (degC) or milliKelvins (mK) It is the measurement of the smallest temshyperature difference that a thermal imager can detect in the presence of electronic noise A 50-mK (005degC) sensitivity is two times as sensitive as a 100-mK (01degC) The NETD can be as important as resolution when deciding what imager to purchase An experienced thermographer can usually distinguish thermal images having as little as a 10 mK NETD difference The lower the thermal sensitivity the more detailed and less noise present on the thermogram This is especially evident in the case when using

small thermal spans Highly sensitive (low-NETD) thermal imagers will show more temperature differences and thus more patterns

The thermoshygrams in Figures 4 and 5 were taken with the same infrashyred imager but tuned to different temperature spans The thermogram in Figure 4 has a span of 3degF which is narshyrower than Figure 5 with a span of 36degF Figure 4 is grainier than Figure 5 If the

Figure 4 ndash A narrow 3degF (17degC) span Figure 5 ndash A wider 36degF (20degC) span imager has 256 disshy

12 bull I n t e r f a c e a u g u s t 2013

crete color levels then for the narshyrow span in Figure 4 each color level would represent 0011degF or 0006degC (6 mK) This is far more sensitive than the 50-mK (005degC) NETD specification for this imager causing increased noise in Figure 4

The infrared imagerrsquos frame rate or capture rate may be an issue if the stabilization of the imager is difficult A low-frame rate (9Hz) makes it difficult to stabilize or freeze the image for capture This is very importshyant if the imager is bouncing due to turbushylence during a flyover (especially helicopter flights) or from a thermographerrsquos hands after too many cups of coffee A 30-Hz or better frame rate should be consideredmdash especially for flyover applications Another imager specification for roof

investigation is detector wavelength Mid-wave detectors (3-5microm) can provide less cold-sky reflection (Figure 18) than the long-wave band of 8-14 microm More of the mid-wave band is absorbed by the atmosphere than the long-wave wavelengths of 8-14 microm This reduces the radiation from the cold sky when using midwave imagers resulting in an attenuated component of the energy reflected (originating from the sky) by the roofing material This is especially useful for low-emissive roofing such as reflective roof coatings

Why DOES ThE WET INSulATION ShOW A PATTERN

The thermal patterns observed on the roof where wet insulation is present are due to material differences in ldquothermal capacityrdquo or ldquoheat capacityrdquo This is the amount of heat (energy) required to raise a unit mass one degree in temperature The chart in Figure 6 provides a graphic representation of specific heat of various materials from gold to water It is clear that water has the highest heat capacity of the materials listed In fact it has such a high-heat capacity that it takes water almost ten times longer to heat than steel Once materials with a high specific heat are heated they stay warmer

Figure 6 ndash Heat capacity of various materials in Btulb degF

longer or cool more slowly When it comes to roofing the heat

capacities of various roofing materials have at least half the heat capacity of water (1 Btulb degF) as shown in Figure 7 In the morning when the sun heats the roofing material the water heats at a slower rate (than the roofing material) conveying a

Figure 7 ndash Heat capacity of various roofing materials in Btulb degF

cooler thermal pattern for the trapped water or wet insulation As the sun sets the heat capacity of the water keeps the water pattern warmer longer providing a heated thermal pattern for the wet insulation

The thermographer can observe thershymal patterns both in the evening just after sunset or in the morning just as the sun is

RCI Foundation ndash United States

Web site wwwrcifoundationorg E-mail foundationrci-onlineorg

The RCI Foundations ndash Supporting The Industry

RCI Foundation ndash Canada

Web site wwwrcifoundationca E-mail inforcifoundationca

a u g u s t 2013 I n t e r f a c e bull 13

crete color levels then for the narshyrow span in Figure 4 each color level would represent 0011degF or 0006degC (6 mK) This is far more sensitive than the 50-mK (005degC) NETD specification for this imager causing increased noise in Figure 4

The infrared imagerrsquos frame rate or capture rate may be an issue if the stabilization of the imager is difficult A low-frame rate (9Hz) makes it difficult to stabilize or freeze the image for capture This is very importshyant if the imager is bouncing due to turbushylence during a flyover (especially helicopter flights) or from a thermographerrsquos hands after too many cups of coffee A 30-Hz or better frame rate should be consideredmdash especially for flyover applications Another imager specification for roof

investigation is detector wavelength Mid-wave detectors (3-5microm) can provide less cold-sky reflection (Figure 18) than the long-wave band of 8-14 microm More of the mid-wave band is absorbed by the atmosphere than the long-wave wavelengths of 8-14 microm This reduces the radiation from the cold sky when using midwave imagers resulting in an attenuated component of the energy reflected (originating from the sky) by the roofing material This is especially useful for low-emissive roofing such as reflective roof coatings

Why DOES ThE WET INSulATION ShOW A PATTERN

The thermal patterns observed on the roof where wet insulation is present are due to material differences in ldquothermal capacityrdquo or ldquoheat capacityrdquo This is the amount of heat (energy) required to raise a unit mass one degree in temperature The chart in Figure 6 provides a graphic representation of specific heat of various materials from gold to water It is clear that water has the highest heat capacity of the materials listed In fact it has such a high-heat capacity that it takes water almost ten times longer to heat than steel Once materials with a high specific heat are heated they stay warmer

Figure 6 ndash Heat capacity of various materials in Btulb degF

longer or cool more slowly When it comes to roofing the heat

capacities of various roofing materials have at least half the heat capacity of water (1 Btulb degF) as shown in Figure 7 In the morning when the sun heats the roofing material the water heats at a slower rate (than the roofing material) conveying a

Figure 7 ndash Heat capacity of various roofing materials in Btulb degF

cooler thermal pattern for the trapped water or wet insulation As the sun sets the heat capacity of the water keeps the water pattern warmer longer providing a heated thermal pattern for the wet insulation

The thermographer can observe thershymal patterns both in the evening just after sunset or in the morning just as the sun is

RCI Foundation ndash United States

Web site wwwrcifoundationorg E-mail foundationrci-onlineorg

The RCI Foundations ndash Supporting The Industry

RCI Foundation ndash Canada

Web site wwwrcifoundationca E-mail inforcifoundationca

a u g u s t 2013 I n t e r f a c e bull 13

Figure 8 ndash Graph showing the temperatures of wet insulation (green points) and dry roof deck (red points)

Figure 9 ndash On-roof viewing of multiple stitched images showing a wide view

rising due to the thermal capacity differences of washyter and roofing material The temperature data shown in Figure 8 indicate temperashyture differences of

Figure 11 ndash Visual image of an on-roof viewing

wet or dry insulation during the day and eveshyning

ROOF INSPECTINg Walk-on inspections

may require a wide-angle lens or the stitchshying of multiple images to provide a wide angle of view shown in Figure 9 as compared to the standard lens shown in Figures 10 and 11

Figure 10 ndash Thermogram of an on-roof viewing Additional thermal patshyterns may be confused for trapped moisture The small hot spots in Figure 10 are due to the high conshyductivity of the fasteners Whenever there is a concern moisture meter testshying (Figures 12-13) or nuclear radioisotopic thermalization12 (Figures 14-15) should be used to confirm the patterning observed by infrared thermography If following the ASTM C1153 standard coring must be performed to confirm the results of the thermogshyraphy inspecshytion

Whenever possible on-roof viewing will benefit from a wider-angle lens or from a higher vantage point such as an adjacent roof

Figure 12 ndash Figure 13 ndash Visual image showing Thermal pattern frozen water and a roof capacitance visible outside of moisture meter (Tramex RWS moisture the frozen puddle meter roof and wall scanner)

14 bull I n t e r f a c e a u g u s t 2013

Figure 14 ndash Wet insulation visible as a cool thermal pattern Figure 15 ndash Technician performing nuclear moisture testing

as shown in Figures 16 and 17 especially when roof access may be difficult or unsafe In addition a birdrsquos-eye view provides the thermographer a much better overview than walking on the surface The same building observed in the roof inspection shown in Figures 16 and 17 is observed in a flyover in Figure 18 Roof flyovers provide opportunities to investigate difficult-to-acshycess roofing as well as multiple roof systems in minutes More area is observed in a single frame from the vantage point of an aircraft above however image resolution is important as shown in the difficult-to-interpret image of Figure 19 Unfortunately ASTM Standard C1153 does not provide guidance for

daytime roof thermography But since the physics do not change thermal patterning can be observed during the day as well as the evening The graph in Figure 8 clearly shows that temperature differences appear throughout the day as well as in the evening Day thermography may be more difficult than evening thermography due to high daytime temperatures overwhelmshying the cool patterns of the wet insulation with hot spots or shadowing as shown in Figures 20-21 The comparison of an evening inspection (Figure 18) and morning inspection (Figures 16-17) of the same area shows the dramatic temperature differences in part due to solar insolation differences of day and night shadowing and night radiation heat transfer

EMISSIVITy AND ANglE Thermal inspections of low emissive surfaces are limited due to the

increase in reflection This is also apparent for on-roof inspections due to the low angle necessary to observe distant areas as shown in Figures 22 to 24 Based on the Lambertrsquos cosine law the radiant intensity observed is directly proportionate to the cosine of the angle (see Figure 25)

Figure 16 ndash Viewing from an adjacent roof

Figure 17 ndash Viewing from an adjacent roof

Figure 18 ndash Flyover of

area shown in Figures 16

Figure 19 ndash Flyover using low-resolution imager digitally zoomed and 17

a u g u s t 2013 I n t e r f a c e bull 15

Figure 20 ndash Cooler patterns may be due to shadowing

Figure 21 ndash Thermal patterns from reflection and shadows

Fronapfel in his 2006 InfraMation article detershymined the emissivity of various building materials and the changes that were induced by adjusting the obsershyvation angle13 For roofing membranes made of ethylene propylene diene monomer (EPDM) the emissivity was observed to change from 095 to 085 when viewed at a 75-degree angle Care should be taken when observing

Figure 22 ndash Reflection due to high angle obscures the roof

Figure 23 ndash Heat reflecting from the building

low-emissive roofing or roof coatings The observed thermal patternshying may be due to reflections and not temperature differences of the material Underdeck inspections can be problematic due to low-emissive

coatings such as radiant barriers but direct view is usually more of an issue since the underdeck is typishycally concealed from view When direct observation can be performed the underdeck results can be dramatic as shown in Figure 26

REPORTINg RESULTS

Roof replacement can be very costly for the building owner By locating a leak or damaged area the cost of repair is conshysiderably less than a new roof Infrared thermography can easily locate and docshyument the leaks proshyviding a clear map to correct the issues without replacement of the whole roof (see Figures 27-29) In addition to the savings of postponshying roof replacement

Figure 24 ndash Reflection from water on the roof surface due to angle and the spectral (smooth) surface of the water

16 bull I n t e r f a c e a u g u s t 2013

Figure 14 ndash Wet insulation visible as a cool thermal pattern Figure 15 ndash Technician performing nuclear moisture testing

as shown in Figures 16 and 17 especially when roof access may be difficult or unsafe In addition a birdrsquos-eye view provides the thermographer a much better overview than walking on the surface The same building observed in the roof inspection shown in Figures 16 and 17 is observed in a flyover in Figure 18 Roof flyovers provide opportunities to investigate difficult-to-acshycess roofing as well as multiple roof systems in minutes More area is observed in a single frame from the vantage point of an aircraft above however image resolution is important as shown in the difficult-to-interpret image of Figure 19 Unfortunately ASTM Standard C1153 does not provide guidance for

daytime roof thermography But since the physics do not change thermal patterning can be observed during the day as well as the evening The graph in Figure 8 clearly shows that temperature differences appear throughout the day as well as in the evening Day thermography may be more difficult than evening thermography due to high daytime temperatures overwhelmshying the cool patterns of the wet insulation with hot spots or shadowing as shown in Figures 20-21 The comparison of an evening inspection (Figure 18) and morning inspection (Figures 16-17) of the same area shows the dramatic temperature differences in part due to solar insolation differences of day and night shadowing and night radiation heat transfer

EMISSIVITy AND ANglE Thermal inspections of low emissive surfaces are limited due to the

increase in reflection This is also apparent for on-roof inspections due to the low angle necessary to observe distant areas as shown in Figures 22 to 24 Based on the Lambertrsquos cosine law the radiant intensity observed is directly proportionate to the cosine of the angle (see Figure 25)

Figure 16 ndash Viewing from an adjacent roof

Figure 17 ndash Viewing from an adjacent roof

Figure 18 ndash Flyover of

area shown in Figures 16

Figure 19 ndash Flyover using low-resolution imager digitally zoomed and 17

a u g u s t 2013 I n t e r f a c e bull 15

Figure 20 ndash Cooler patterns may be due to shadowing

Figure 21 ndash Thermal patterns from reflection and shadows

Fronapfel in his 2006 InfraMation article detershymined the emissivity of various building materials and the changes that were induced by adjusting the obsershyvation angle13 For roofing membranes made of ethylene propylene diene monomer (EPDM) the emissivity was observed to change from 095 to 085 when viewed at a 75-degree angle Care should be taken when observing

Figure 22 ndash Reflection due to high angle obscures the roof

Figure 23 ndash Heat reflecting from the building

low-emissive roofing or roof coatings The observed thermal patternshying may be due to reflections and not temperature differences of the material Underdeck inspections can be problematic due to low-emissive

coatings such as radiant barriers but direct view is usually more of an issue since the underdeck is typishycally concealed from view When direct observation can be performed the underdeck results can be dramatic as shown in Figure 26

REPORTINg RESULTS

Roof replacement can be very costly for the building owner By locating a leak or damaged area the cost of repair is conshysiderably less than a new roof Infrared thermography can easily locate and docshyument the leaks proshyviding a clear map to correct the issues without replacement of the whole roof (see Figures 27-29) In addition to the savings of postponshying roof replacement

Figure 24 ndash Reflection from water on the roof surface due to angle and the spectral (smooth) surface of the water

16 bull I n t e r f a c e a u g u s t 2013

Figure 20 ndash Cooler patterns may be due to shadowing

Figure 21 ndash Thermal patterns from reflection and shadows

Fronapfel in his 2006 InfraMation article detershymined the emissivity of various building materials and the changes that were induced by adjusting the obsershyvation angle13 For roofing membranes made of ethylene propylene diene monomer (EPDM) the emissivity was observed to change from 095 to 085 when viewed at a 75-degree angle Care should be taken when observing

Figure 22 ndash Reflection due to high angle obscures the roof

Figure 23 ndash Heat reflecting from the building

low-emissive roofing or roof coatings The observed thermal patternshying may be due to reflections and not temperature differences of the material Underdeck inspections can be problematic due to low-emissive

coatings such as radiant barriers but direct view is usually more of an issue since the underdeck is typishycally concealed from view When direct observation can be performed the underdeck results can be dramatic as shown in Figure 26

REPORTINg RESULTS

Roof replacement can be very costly for the building owner By locating a leak or damaged area the cost of repair is conshysiderably less than a new roof Infrared thermography can easily locate and docshyument the leaks proshyviding a clear map to correct the issues without replacement of the whole roof (see Figures 27-29) In addition to the savings of postponshying roof replacement

Figure 24 ndash Reflection from water on the roof surface due to angle and the spectral (smooth) surface of the water

16 bull I n t e r f a c e a u g u s t 2013

RCI-50-Half-Horiztonalindd 1 12112012 51541 PM

Figure 25 ndash Reflection due to high angle obscures the patterns radiating from the roof14

energy costs will be reduced Wet fiberglass insulation is 14 times more conductive than dry insulation Locating the wet insulation and replacing it will save heating and coolshying costs for the building Because of these effective cost-saving measures and ease of mapping wet insulation infrared imagers are the best method available today to locate a roof leak

Figure 26 ndash Thermal pattern visible at the underside of the deck

IMPORTANT CONSIDERATIONS WhEN INSPECTINg

The foremost consideration for a roof investigation is safety for the personnel Climbing onto the roof presents a clear safety hazard of falling In my personal comshymunications with building investigators Irsquove heard from many survivors falling from ladders and through decayed roofing many

becoming physically disabled due to the falls We all believe it will not happen to us but it is a reality for many Below is a simple (but not all-exclusive) list of important safeshyty considerations bull Always use proper restraints and

proper safety equipment during inspections

bull Always inspect the underside of the

a u g u s t 2013 I n t e r f a c e bull 17

Figure 27 ndash Mapping the location of the moisture

roof deck to ensure its condition before going onto the roof bull Always team up during a roof inspection bull Make sure an emergency contact plan is in place

mdash Does your cell phone have coverage mdash Who is the safety coordinator for the building mdash Get local emergency numbers and your specific address especially

if you use a cell phone which may not be tracked to a location bull Consider the surrounding buildings and areas Security for adjacent areas may require notification Contact adjacent building occupants and the local police so they are aware of your investigation You do not want to be considered a sniper and they may prove to be valuable marketing contacts for future work

The environment is an important consideration During inspectionmdash especially during evening inspectionsmdashcondensation or ice can occur on the roof surface creating slick unsafe conditions as well as preventing thermal observations Figure 12 shows a warmer patterning (due to wet insulation) adjacent to a frozen area of water The ice is also trapping water below its surface showing a warm pattern conducting through the ice Always observe the weather reports for the possibility of rain or clouds that could inhibit or prevent the use of thermography Consider multiple investigations to observe the roof during or immediately following rain event(s) to determine possible ponding and proper drainage of the surface Inspections during or immediateshyly following rain event(s) on the underside of the roof could allow detection of an active water intrusion into the building

18 bull I n t e r f a c e a u g u s t 2013

800-771-1711

Figures 28 and 29 ndash Thermal images

locate the wet areas

useful at providshying qualification levels and expeshyrience requireshyments it tends not to provide enough guidance for the complex specific thermog shyraphy applications such as buildings or roofing Both require extensive background in building sciences and construction

The ASTM C1153 standard notes the following very important environmental parameters bull No appreciable precipitation for the previous 48 hours Infrared cannot see through water

bull No standing water bull Wind less than 25 kmh (15 mph) to

prevent convective heat loss of the thermal patterns

bull Direct sunshine on the roof during the day

bull At least 18˚F (10˚C) between inside and outside of the roof if there is little sun

Not all thermographers are competent to perform roof inspections Training is importshyant for all thermographers with most US training organizations using the American Society for Nondestructive Testing Inc (ASNT) Recommended Practices ASNT SNTshyTC-1A as a guide15 Though this guide is universally cited for training guidance and

to provide compeshytence for this application of thermography

The Canadian National Master Specishyfication (NMS) is providing a new approach to the complex certification requirements for thermography by developing specificashytions for electrical mechanical roofing and building envelope industries16 Others are working on international standards that provide more guidance on application-speshycific qualifications and certification requireshyments for thermography It is clear that proper equipment training and experience are important for competency in the applishycation of roof thermography

SuMMARy Infrared thermography is the conversion

of invisible infrared electromagnetic radishyation into a visible image It is important to understand image resolution and thershymal sensitivity in order to choose the right imager for an application Lens types such as wide-angle normal or telephoto are also considerations The high-heat capacity

a u g u s t 2013 I n t e r f a c e bull 19

Figure 27 ndash Mapping the location of the moisture

roof deck to ensure its condition before going onto the roof bull Always team up during a roof inspection bull Make sure an emergency contact plan is in place

mdash Does your cell phone have coverage mdash Who is the safety coordinator for the building mdash Get local emergency numbers and your specific address especially

if you use a cell phone which may not be tracked to a location bull Consider the surrounding buildings and areas Security for adjacent areas may require notification Contact adjacent building occupants and the local police so they are aware of your investigation You do not want to be considered a sniper and they may prove to be valuable marketing contacts for future work

The environment is an important consideration During inspectionmdash especially during evening inspectionsmdashcondensation or ice can occur on the roof surface creating slick unsafe conditions as well as preventing thermal observations Figure 12 shows a warmer patterning (due to wet insulation) adjacent to a frozen area of water The ice is also trapping water below its surface showing a warm pattern conducting through the ice Always observe the weather reports for the possibility of rain or clouds that could inhibit or prevent the use of thermography Consider multiple investigations to observe the roof during or immediately following rain event(s) to determine possible ponding and proper drainage of the surface Inspections during or immediateshyly following rain event(s) on the underside of the roof could allow detection of an active water intrusion into the building

18 bull I n t e r f a c e a u g u s t 2013

800-771-1711

Figures 28 and 29 ndash Thermal images

locate the wet areas

useful at providshying qualification levels and expeshyrience requireshyments it tends not to provide enough guidance for the complex specific thermog shyraphy applications such as buildings or roofing Both require extensive background in building sciences and construction

The ASTM C1153 standard notes the following very important environmental parameters bull No appreciable precipitation for the previous 48 hours Infrared cannot see through water

bull No standing water bull Wind less than 25 kmh (15 mph) to

prevent convective heat loss of the thermal patterns

bull Direct sunshine on the roof during the day

bull At least 18˚F (10˚C) between inside and outside of the roof if there is little sun

Not all thermographers are competent to perform roof inspections Training is importshyant for all thermographers with most US training organizations using the American Society for Nondestructive Testing Inc (ASNT) Recommended Practices ASNT SNTshyTC-1A as a guide15 Though this guide is universally cited for training guidance and

to provide compeshytence for this application of thermography

The Canadian National Master Specishyfication (NMS) is providing a new approach to the complex certification requirements for thermography by developing specificashytions for electrical mechanical roofing and building envelope industries16 Others are working on international standards that provide more guidance on application-speshycific qualifications and certification requireshyments for thermography It is clear that proper equipment training and experience are important for competency in the applishycation of roof thermography

SuMMARy Infrared thermography is the conversion

of invisible infrared electromagnetic radishyation into a visible image It is important to understand image resolution and thershymal sensitivity in order to choose the right imager for an application Lens types such as wide-angle normal or telephoto are also considerations The high-heat capacity

a u g u s t 2013 I n t e r f a c e bull 19

800-771-1711

Figures 28 and 29 ndash Thermal images

locate the wet areas

useful at providshying qualification levels and expeshyrience requireshyments it tends not to provide enough guidance for the complex specific thermog shyraphy applications such as buildings or roofing Both require extensive background in building sciences and construction

The ASTM C1153 standard notes the following very important environmental parameters bull No appreciable precipitation for the previous 48 hours Infrared cannot see through water

bull No standing water bull Wind less than 25 kmh (15 mph) to

prevent convective heat loss of the thermal patterns

bull Direct sunshine on the roof during the day

bull At least 18˚F (10˚C) between inside and outside of the roof if there is little sun

Not all thermographers are competent to perform roof inspections Training is importshyant for all thermographers with most US training organizations using the American Society for Nondestructive Testing Inc (ASNT) Recommended Practices ASNT SNTshyTC-1A as a guide15 Though this guide is universally cited for training guidance and

to provide compeshytence for this application of thermography

The Canadian National Master Specishyfication (NMS) is providing a new approach to the complex certification requirements for thermography by developing specificashytions for electrical mechanical roofing and building envelope industries16 Others are working on international standards that provide more guidance on application-speshycific qualifications and certification requireshyments for thermography It is clear that proper equipment training and experience are important for competency in the applishycation of roof thermography

SuMMARy Infrared thermography is the conversion

of invisible infrared electromagnetic radishyation into a visible image It is important to understand image resolution and thershymal sensitivity in order to choose the right imager for an application Lens types such as wide-angle normal or telephoto are also considerations The high-heat capacity

a u g u s t 2013 I n t e r f a c e bull 19

of water provides the means for observing thermal patterning of trapped moisture within the roof system

ISO 67811983 (Thermal insulation ndash Qualitative detection of thermal irregularishyties in building envelopes ndash infrared method) and the similar ASTM C1153 standard are currently the only available standards but are outdated due to fast-paced technologshyical advances in thermal imagers These standards provide good guidance for the roof thermographer but little guidance for daytime thermography New or updated standards are needed as it is clear that proper equipment training and experience are important for competency in the applishycation of roof thermography

Locating wet insulation will save the building owner the cost of a total roof replacement Energy savings are also achieved by replacing the highly conductive wet insulation thereby saving on heating and cooling costs Because of these effective cost-saving techniques infrared imagers are the best method available today to evalshyuate map and locate roof leaks

Major advantages of an infrared roof moisture survey are bull Locates water-damaged insulation

quickly and accurately bull Identifies small problems before they

become serious and more costly to repair

bull Eliminates unnecessary replaceshyment of good roof

bull Documents problems before the warranty expires

bull Greatly extends the life of the roof

A roof moisture survey should be carried out bull Prior to acceptance of a new roof

system or during a buildingrsquos comshymissioning process

bull Before any existing warranties expire bull Before acquiring a new building bull Before roofing over existing roofing bull For planned maintenance purshy

poses

REFERENCES 1 Kathryn Barker Knettel ldquoThermoshy

graphic Anomalies in Roof Memshybranes Wet Insulation or False Indicationsrdquo InfraMation Proceedshyings Volume 1 2000

2 Kathryn Barker Knettel ldquoThermoshygraphics Involving Rubber-Based Cap-Sheet Membranesrdquo InfraMation Proceedings Volume 3 2002

3 Palani Subramanian ldquoAn Application of Infrared Thermography ndash Roofing Surveyrdquo InfraMation Proceedings Volume 6 2005

4 David Khudaverdian ldquoA Global Strategy for Evaluating Building Roof Performance and Diagnosing Moisture Intrusion Into Roofing Systems Using Infrared Thermo-graphy and Other Diagnostic Toolsrdquo InfraMation Proceedings Volume 8 2007

5 Antonio Colantonio and Scott Wood ldquoDetection of Moisture Within Building Enclosures by Interior and Exterior Thermographic Inspectionsrdquo InfraMation Proceedings Volume 9 2008

20 bull I n t e r f a c e a u g u s t 2013

6 Ronald D Lucier ldquoDaytime Infrared Roof Inspectionsrdquo Interface RCI Inc August 2004

7 Gregory Stockton ldquoSelected Applications and Methodology for Aerial Infrared Thermographyrdquo InfraMation Proceedings Volume 2 2001

8 Gregory Stockton ldquoAdvances in Aerial IR Applicationsrdquo InfraMation Proceedings Volume 8 2007

9 Gregory Stockton ldquoMethodologies for Finding Analyzing and Prioritizing Moisture Problems in Roofing Materials Using Infrared Thermal Imagingrdquo IRINFO 2013

10 ASTM C-1153 [97 (2010)] ldquoStandard Practice for the Location of Wet Insulation in Roofing Systems Using Infrared Imagingrdquo American Society for Testing and Materials www astmorg

11 Electrophysics Resource Center Infrared Inspection White Paper ldquoUnderstanding Infrared Imager Thermal Image Qualityrdquo

Electrophysics Infrared Inspection 14 Alex Ryer Light Measurement 2009 Handbook International Light Inc

12 ldquoDetection and Location of Latent 1998 Moisture in Building Roofing 15 Sandy Sanor ldquoThe Professional Systems by Nuclear Radioisotopic Infrared Thermographerrdquo Infra-Thermalizationrdquo ANSISPRIRCI Mation Proceedings Volume 2 2001 NT-1 July 20 2012 16 Antonio Colantonio ldquoSpecifying

13 Edward Fronapfel ldquoEmissivity Infrared Thermographic Services Measurements of Common Construc- for Large Buildingsrdquo InfraMation tion Materialsrdquo InfraMation Pro- Proceedings Volume 8 2007 ceedings Volume 7 2006

Scott Wood

Scott Wood president of Scott Wood Associates LLC is an Air Barrier Association of America (ABAA) auditor and a Level III thermographer Starting in 2003 he created building science thermography classes that he has since taught to thousands He is a founding member and treasurer of the International Association of Certified Thermographers (IACT) company advisor for ēssess inc an active voting member for ASTM International C16 committee and a member of the National Association of Commercial Building Inspectors and Thermographers (NACBI) National Institute of Building Sciences (NIBS) and the Seattle Building Enclosure Council (SeaBEC)

a u g u s t 2013 I n t e r f a c e bull 21

6 Ronald D Lucier ldquoDaytime Infrared Roof Inspectionsrdquo Interface RCI Inc August 2004

7 Gregory Stockton ldquoSelected Applications and Methodology for Aerial Infrared Thermographyrdquo InfraMation Proceedings Volume 2 2001

8 Gregory Stockton ldquoAdvances in Aerial IR Applicationsrdquo InfraMation Proceedings Volume 8 2007

9 Gregory Stockton ldquoMethodologies for Finding Analyzing and Prioritizing Moisture Problems in Roofing Materials Using Infrared Thermal Imagingrdquo IRINFO 2013

10 ASTM C-1153 [97 (2010)] ldquoStandard Practice for the Location of Wet Insulation in Roofing Systems Using Infrared Imagingrdquo American Society for Testing and Materials www astmorg

11 Electrophysics Resource Center Infrared Inspection White Paper ldquoUnderstanding Infrared Imager Thermal Image Qualityrdquo

Electrophysics Infrared Inspection 14 Alex Ryer Light Measurement 2009 Handbook International Light Inc

12 ldquoDetection and Location of Latent 1998 Moisture in Building Roofing 15 Sandy Sanor ldquoThe Professional Systems by Nuclear Radioisotopic Infrared Thermographerrdquo Infra-Thermalizationrdquo ANSISPRIRCI Mation Proceedings Volume 2 2001 NT-1 July 20 2012 16 Antonio Colantonio ldquoSpecifying

13 Edward Fronapfel ldquoEmissivity Infrared Thermographic Services Measurements of Common Construc- for Large Buildingsrdquo InfraMation tion Materialsrdquo InfraMation Pro- Proceedings Volume 8 2007 ceedings Volume 7 2006

Scott Wood

Scott Wood president of Scott Wood Associates LLC is an Air Barrier Association of America (ABAA) auditor and a Level III thermographer Starting in 2003 he created building science thermography classes that he has since taught to thousands He is a founding member and treasurer of the International Association of Certified Thermographers (IACT) company advisor for ēssess inc an active voting member for ASTM International C16 committee and a member of the National Association of Commercial Building Inspectors and Thermographers (NACBI) National Institute of Building Sciences (NIBS) and the Seattle Building Enclosure Council (SeaBEC)

a u g u s t 2013 I n t e r f a c e bull 21